> The United States is a signatory to an international treaty that stipulates that exploration must be conducted in a manner that avoids of the transportation of living organisms to celestial bodies.
First of all the US is part of a treaty, so if we do introduce organisms to other plants we are violating the treaty.
> We wouldn't want to go to Mars and "discover" life - only to figure out later that we brought it with us! Scientists also want to study the planet and any life that might be there in its original "pristine state."
Ultimately I guess it comes down to why you are sending something to space. If your goal is science then contaminating the planetary environment with organisms is not great. If your goal is colonization (which I guess is SpaceX goal) then you probably wouldn't care. But I still think it's something that should be considered.